Magnetic linear position sensor

Abstract

A magnetic linear position sensor includes an array of N number of magnets. The array of magnets is distributed along a line to form a magnetic field relay along the line. The sizes and positions of the magnets in the array of magnets are symmetric along the line, and the size of the magnets decreases from the sides of the array of magnets towards the center of the array of magnets. The magnetic linear position sensor further includes a magnetic field sensor spaced apart and positioned above the array of magnets. The magnetic field sensor moves back and forth over the array of magnets to sense the magnetic field of the array of magnets.

What is claimed is: 
     
       1. A magnetic linear position sensor comprising:
 an array of N number of magnets distributed along a line to form a magnetic field relay along the line, the array of magnets including a first set of N1 magnets and a second set of N2, where N=N1+N2, the first set of N1 magnets being positioned on one side of a center of the array of magnets and the second set of N2 magnets being positioned on the other side of the center of the array of magnets, the size of the magnets decreasing from the sides of the array of magnets towards the center of the array of magnets; and 
 a magnetic field sensor spaced apart and positioned above the array of magnets, 
 wherein the magnetic field sensor moves back and forth over the array of magnets to sense the magnetic field of the array of magnets, the magnetic linear position sensor having performance characteristics that include a sensing range, a linearity of the magnets, a size of each magnet, and a sensor signal range, and 
 wherein the performance characteristics are compared to sensor design characteristics to determine if the sensing range exceeds a minimum range, if the linearity is less than a maximum allowable value, if the sensor signal range exceeds a minimum value and is less than a maximum value, and if the total magnet size is less than a maximum value such that an optimal configuration of the array of magnets is set if the performance characteristics meet the sensor design objectives. 
 
     
     
       2. The magnetic linear position sensor of  claim 1  wherein the magnetic field sensor is a Hall element. 
     
     
       3. The magnetic linear position sensor of  claim 1  wherein the size of each magnet is defined by a respective width, length, and height. 
     
     
       4. The magnetic linear position sensor of  claim 3  wherein the lengths of the magnets decrease from the sides of the array towards the center of the array. 
     
     
       5. The magnetic linear position sensor of  claim 3  wherein the widths of the magnets decrease from the side of the array towards the center of the array. 
     
     
       6. The magnetic linear position sensor of  claim 1  wherein N1=N2 and N is an even number. 
     
     
       7. The magnetic linear position sensor of  claim 1  wherein N is an odd number. 
     
     
       8. The magnetic linear position sensor of  claim 1  wherein N≧3. 
     
     
       9. The magnetic linear position sensor of  claim 1  wherein N=6. 
     
     
       10. The magnetic linear position sensor of  claim 1  wherein the magnetic linear position sensor is a fork position sensor in a motor vehicle transmission. 
     
     
       11. A method of optimizing a magnetic linear position sensor, the method comprising:
 setting initial values of an array of N number of magnets, the initial values including each magnets length, width, height and position, the array of N number of magnets being distributed along a line to form a magnetic field relay along the line, the array of magnets including a first set of N1 magnets and a second set of N2 magnets, where N=N1+N2, the first set of N1 magnets being positioned on one side of a center of the array of magnets and the second set of N2 magnets being positioned on the other side of the center of the array of magnets; 
 simulating the performance of the magnetic linear position sensor, the simulation including a magnetic field sensor spaced apart and positioned above the array of magnets, the magnetic field sensor moving back and forth over the array of magnets to sense the magnetic field of the array of magnets, the magnetic linear position sensor performance including the sensing range, the linearity of the magnets, the size of each magnet, and the sensor signal range; 
 comparing results of the simulation of the performance of the magnetic linear position sensor with sensor design objectives, comparing results including determining if the sensing signal range exceeds a minimum range, if the linearity is less than a maximum allowable value, if the sensor signal range exceeds a minimum value and is less than a maximum value, and if the total magnet size is less than a maximum value; 
 setting an optimal configuration of the array of magnets if the simulation results meet the sensor design objectives; and 
 optimizing the array of magnets with a new set of length, width, height, and position for each magnet and resetting the initial values of the array of magnets with the new set of length, width, height, and position for each magnet. 
 
     
     
       12. The method of  claim 11  wherein the sizes and positions of the magnets in the array of magnets is symmetric along the line, the size of the magnets decreasing from the sides of the array of magnets towards the center of the array of magnets. 
     
     
       13. The method of  claim 11  wherein the lengths of the magnets decrease from the sides of the array towards the center of the array. 
     
     
       14. The method of  claim 13  wherein the widths of the magnets decrease from the side of the array towards the center of the array. 
     
     
       15. The method of  claim 11  wherein N1=N2 and N is an even number. 
     
     
       16. The method of  claim 11  wherein N≧3. 
     
     
       17. The method of  claim 11  wherein N=6. 
     
     
       18. The method of  claim 11  wherein the magnetic linear position sensor is a fork position sensor in a motor vehicle transmission.